Fabrication of semiconductor devices with air gaps for ultra low capacitance interconnections and methods of making same

ABSTRACT

A method of forming an air gap or gaps within solid structures and specifically semiconductor structures to reduce capacitive coupling between electrical elements such as metal lines, wherein a sacrificial material is used to occupy a closed interior volume in a semiconductor structure is disclosed. The sacrificial material is caused to decompose into one or more gaseous decomposition products which are removed, in one embodiment by diffusion, through an overcoat layer. The decomposition of the sacrificial material leaves an air gap or gaps at the closed interior volume previously occupied by the sacrificial material. The air gaps may be disposed between electrical leads to minimize capacitive coupling therebetween.  
     Also disclosed are methods of forming multi-level air gaps and methods or forming over-coated conductive lines or leads wherein a portion of the overcoating is in contact with at least one air gap.

RELATED APPLICATION DATA

[0001] This application is a division of U.S. patent application Ser.No. 09/945,305, filed Aug. 31, 2001, now U.S. Pat. No. 6,610,593, thatclaims priority to previously filed U.S. Provisional Application No.60/229,589, filed on Aug. 31, 2000, entitled “Compositions forFabrication of Semiconductor Devices with Air Gaps for Ultra LowCapacitance Interconnections and Methods of Making Same”; U.S.Provisional Application No. 60/229,660, filed on Aug. 31, 2000, entitled“Compositions for Fabrication of Semiconductor Devices with Multi-LevelAir Gaps for Ultra Low Capacitance Interconnections and Methods ofMaking Same”; and U.S. Provisional Application No. 60/229,658, filed onAug. 31, 2000 entitled “Fabrication of Semiconductor Devices with AirGaps for Ultra Low Capacitance Interconnections and Methods of MakingSame.” All of the aforesaid applications are incorporated herein byreference in their entireties.

FIELD OF THE INVENTION

[0002] The invention herein described relates generally to thefabrication of semiconductor devices and more specifically to suchdevices that use air gaps and/or multi-level air gaps to reducecapacitive coupling between conductors in such devices. Additionally,the invention herein described relates to the fabrication ofsemiconductor devices which can contain overcoated conductive lines orleads which are at least partially adjacent to one or more air gaps.

BACKGROUND OF THE INVENTION

[0003] As a consequence of the progress made in integrated circuittechnology, the spacing between the metal lines on any given plane of anintegrated circuit has become less and less, now extending into thesubmicrometer range. By reducing the spacing between conductive membersin the integrated circuit, an increase in capacitive coupling occurs.This increase in capacitive coupling causes greater crosstalk, highercapacitive losses and increased RC time constant.

[0004] In order to reduce capacitive coupling, much effort has beendirected toward developing low dielectric constant (low-K) materials toreplace conventional dielectric materials that are interposed betweenthe metal lines on a given layer and between layers. Many conventionalelectronic insulators have dielectric constants in the 3.5 to 4.2 range.For example, silicon dioxide has a dielectric constant of 4.2 andpolyimides typically have dielectric constants from 2.9 to 3.5. Someadvanced polymers have dielectric constants in the 2.5 to 3.0 range.Materials in the 1.8 to 2.5 range are also known, but such materialshave had associated therewith severe processing, cost and materialsproblems.

[0005] The lowest possible, or ideal, dielectric constant is 1.0, whichis the dielectric constant of a vacuum. Air is almost as good with adielectric constant of 1.001. With this recognition of the lowdielectric constant of air, attempts have been made to fabricatesemiconductor devices with air gaps between metal leads to reduce thecapacitive coupling between the electrically conducting members. The airgap forming techniques that have been developed have varying degrees ofcomplexity.

[0006] U.S. Pat. No. 4,987,101 describes a method and structure forproviding an insulating electrical space between two lines on a layer ofmaterial or between lines on adjacent superposed layers of material. Abase member is formed having a plurality of support members extendingupwardly from the base member. A removable material is deposited on thebase member and around the support members. A cap member of insulatingmaterial is then disposed over said support members and the removablematerial. Access openings are formed in at least one of the base memberor the cap member communicating with the removable material. Theremovable material is removed through the access openings to therebydefine a space between the cap member and the base member and betweenthe support members. During this step a partial vacuum (in which someinert gas may be dispersed) may be created in the space vacated by theremovable material. The access openings are then filled in so as toprovide a sealed space between the cap member and the base member whichhas a very low dielectric constant.

[0007] U.S. Pat. No. 5,324,683 describes several techniques for formingair gaps or regions in a semiconductor device. The air regions areformed by either selectively removing a sacrificial spacer or byselectively removing a sacrificial layer. The air regions are sealed,enclosed or isolated by either a selective growth process or by anon-conformal deposition technique. The air regions may be formed underany pressure, gas concentration or processing condition.

[0008] The techniques disclosed in the aforesaid patents rely on holesor other passageways for effecting removal of the sacrificial material.In U.S. Pat. No. 5,461,003, a sacrificial material is removed through aporous dielectric layer. According to this patent, metal leads areformed on a substrate, after which a disposable solid layer is depositedon the metal leads and substrate. The disposable solid layer is thenetched back to expose the tops of the metal leads. Then a porousdielectric layer is deposited over the metal leads and disposable layer.This is followed by removal of the disposable layer which is said to bepreferably accomplished by exposing the device to oxygen oroxygen-plasma at a high temperature (>100° C.) to vaporize, or burn off,the disposable layer. The oxygen moves through the porous dielectriclayer to reach and react with the disposable layer and thereby convertit to a gas that moves back out of the porous dielectric layer. Uponremoval of the disposable layer, air gaps are left to provide a lowdielectric constant. Finally, a non-porous dielectric layer is depositedon top of the porous dielectric layer to seal the porous dielectriclayer from moisture, provide improved structural support and thermalconductivity, and passivate the porous dielectric layer. This procedureresults in an air gap that does not extend the full height of theadjacent metal leads or lines. The '003 patent discloses a modifiedmethod to remedy this and increase the process margin. This modifiedmethod involves a further process step wherein an oxide layer is formedon top of the metal leads so that the disposable dielectric layer canextend higher than the metal leads.

[0009] It is also noted that the exposure of the device to an oxygenplasma which must diffuse through a porous layer is not onlyinefficient, it also exposes other elements of the device to apotentially damaging oxygen plasma for an extended period of time. Inparticular, exposure of oxygen plasma to copper lines can provedeleterious. Copper is becoming an increasingly important metal insemiconductor manufacturing due to its lower resistivity when comparedto aluminum.

[0010] WO 98/32169 describes a method of forming an air gap or gapswithin solid structures and specifically semiconductor structures toreduce capacitive coupling between electrical elements such as metallines. According to WO 98/32169 a method of forming an air gap in asemiconductor structure comprises the steps of (i) using anorbornene-type polymer as a sacrificial material to occupy a closedinterior volume in a semiconductor structure; (ii) causing thesacrificial material to decompose (preferably self-decompose uponthermal treatment) into one or more gaseous decomposition products; and(iii) removing at least one of the one or more gaseous decompositionproducts by passage through at least one solid layer contiguous to theinterior volume. The decomposition of the sacrificial material leaves anair gap at the closed interior volume previously occupied by thenorbornene-type polymer.

[0011] WO 98/32169 further describes that the solid layer is adielectric material through which at least one of the one or moregaseous decomposition products can pass by diffusion under conditionsnot detrimental to the semiconductor structure. Finally, WO 98/32169also discloses production methods which can utilize a wide range ofsacrificial materials instead of only a norbornene-type polymer.

SUMMARY OF THE INVENTION

[0012] The present invention provides a method of forming an air gap orgaps (or multi level structures having such gaps) within solidstructures and specifically semiconductor structures to reducecapacitive coupling between electrical elements such as metal lines.Also disclosed is a method which enables the production of overcoatedconductive lines or leads. Such methods overcome one or more of thedrawbacks associated with the aforesaid prior attempts to reducecapacitive coupling in semiconductor structures such as integratedcircuits and packages.

[0013] For example, in some instances it is advantageous to utilize asacrificial material which is less costly, easier to process or “work”with, and has a lower decomposition temperature. The present inventionprovides such advantages via methods which enable to formation and/orproduction of structures having air gaps produced utilizingpolycarbonates and/or polymethyl methacrylates.

[0014] According to one aspect of the invention, a method of forming anair gap within a semiconductor structure comprises the steps of: (i)using a sacrificial material to occupy a closed interior volume in asemiconductor structure; (ii) causing the sacrificial material todecompose into one or more gaseous decomposition products; and (iii)removing at least one of the one or more gaseous decomposition productsby passage through at least one solid layer contiguous to the interiorvolume, wherein the decomposition of the sacrificial material leaves anair gap at the closed interior volume previously occupied thereby, andthe sacrificial material comprises a polymer composition selected fromone or more polycarbonate polymers, polyester polymers, polyetherpolymers, methacrylate polymers, acrylate polymers, or mixtures thereof.

[0015] In accordance with another aspect of the invention, a method offorming one or more air gaps in a semiconductor structure comprises thesteps of: (I) forming a patterned layer of sacrificial material on asubstrate corresponding to a pattern of one or more gaps to be formed inthe semiconductor structure; (II) depositing a second material on thesubstrate within regions bordered by the sacrificial material; (III)forming an overcoat layer of material overlying the patterned layer ofsacrificial material and second material in the regions bordered by thesacrificial material; (IV) causing the sacrificial material to decomposeinto one or more gaseous decomposition products; and (V) removing atleast one of the one or more gaseous decomposition products by passagethrough the overcoat layer so that one or more air gaps are formedwithin the semiconductor structure, wherein the sacrificial material isa polymer composition selected from one or more polycarbonate polymers,polyester polymers, polyether polymers, methacrylate polymers, acrylatepolymers, or mixtures thereof.

[0016] In accordance with another aspect of the invention, a method offorming air gaps within a semiconductor structure comprises the stepsof: using at least one sacrificial material to occupy simultaneously orsequentially at least two closed interior volumes in a semiconductorstructure, wherein the at least two closed interior volumes are ondifferent levels of the semiconductor structure; causing the at leastone sacrificial material occupying the at least two closed interiorvolumes to decompose either simultaneously or sequentially into one ormore gaseous decomposition products; and removing at least one of theone or more gaseous decomposition products by passage through at leastone solid layer contiguous to the interior volume.

[0017] In accordance with another aspect of the invention, a method offorming one or more air gaps in a semiconductor structure comprises thesteps of: (A) forming a patterned layer of a first sacrificial materialon one side of a substrate corresponding to a pattern of one or moregaps to be formed in the semiconductor structure; (B) depositing asecond material on the substrate within regions bordered by the firstsacrificial material; (C) forming a first overcoat layer of materialoverlying the patterned layer of the first sacrificial material and thesecond material in the regions bordered by the first sacrificialmaterial; (D) causing the first sacrificial material to decompose intoone or more gaseous decomposition products; (E) removing at least one ofthe one or more gaseous decomposition products by passage through thefirst overcoat layer so that one or more air gaps are formed within thesemiconductor structure; (F) forming a patterned layer of a secondsacrificial material on the first overcoat layer corresponding to apattern of one or more gaps to be formed in the semiconductor structure;(G) depositing a third material on the first overcoat layer substratewithin regions bordered by the second sacrificial material; (H) forminga second overcoat layer of material overlying the patterned layer of thesecond sacrificial material and the third material in the regionsbordered by the second sacrificial material; (I) causing the secondsacrificial material to decompose into one or more gaseous decompositionproducts; and (J) removing at least one of the one or more gaseousdecomposition products by passage through the overcoat layers so thatone or more air gaps are formed within the semiconductor structure,wherein the first and second sacrificial materials are independentlyselected from one or more polycarbonate polymers, polyester polymers,polyether polymers, methacrylate polymers, acrylate polymers, ormixtures thereof.

[0018] In accordance with another aspect of the invention, a method offorming one or more air gaps in a semiconductor structure comprises thesteps of: (A) forming a patterned layer of a first sacrificial materialon one side of a substrate corresponding to a pattern of one or moregaps to be formed in the semiconductor structure; (B) depositing asecond material on the substrate within regions bordered by the firstsacrificial material; (C-1) forming a first overcoat layer of materialoverlying the patterned layer of the first sacrificial material and thesecond material in the regions bordered by the first sacrificialmaterial; (C-2) forming a patterned layer of a second sacrificialmaterial on the first overcoat layer corresponding to a pattern of oneor more gaps to be formed in the semiconductor structure; (C-3)depositing a third material on the first overcoat layer within regionsbordered by the second sacrificial material; (C-4) forming a secondovercoat layer of material overlying the patterned layer of the secondsacrificial material and the third material in the regions bordered bythe second sacrificial material; (D′) causing the first and secondsacrificial materials to decompose into one or more gaseousdecomposition products; and (E′) removing at least one of the one ormore gaseous decomposition products by passage through the overcoatlayers so that one or more air gaps are formed within the semiconductorstructure, wherein the first and second sacrificial materials areindependently selected from one or more norbornene polymers,polycarbonate polymers, polyester polymers, polyether polymers,methacrylate polymers, acrylate polymers, or mixtures thereof.

[0019] In accordance with another aspect of the invention, a method offorming one or more air gaps in a semiconductor structure comprises thesteps of: using a sacrificial material to occupy at least one firstclosed interior volume in a semiconductor structure and using aconductive material to occupy at least one second closed interior volumein a semiconductor structure, the at least one first closed interiorvolume and the at least one second closed interior volume defining atleast one gap therebetween; forming an overcoat layer of material on thesacrificial material and the conductive material with the overcoatmaterial extending into the at least one gap; causing the sacrificialmaterial to decompose into one or more gaseous decomposition products;and removing at least one of the one or more gaseous decompositionproducts by passage through the first overcoat layer so that one or moreair gaps are formed within the semiconductor structure, thereby yieldingovercoated conductive structures.

[0020] According to yet another aspect of the invention, a semiconductordevice having at least one air gap therein comprises: a substrate; atleast one conductive line or lead; at least one air gap; and an overcoatlayer, wherein the at least one air gap is produced in accordance withany one of the methods disclosed herein.

[0021] According to yet another aspect of the invention, a semiconductorstructure comprises: a substrate; a sacrificial material supported onthe substrate; a conductive material supported on the substrate andspaced apart from the sacrificial material; an overcoat layerovercoating the sacrificial material and the conductive material andextending into the one or more spaces between the sacrificial materialand the conductive material.

[0022] According to yet another aspect of the invention, a semiconductorstructure comprises: a substrate; a sacrificial material supported onthe substrate; a conductive material supported on the substrate andspaced apart from the sacrificial material; an overcoat layerovercoating the sacrificial material and the conductive material andextending into the one or more spaces between the sacrificial materialand the conductive material, wherein the sacrificial material has beenremoved by decomposition through the overcoat layer.

[0023] To the accomplishment of the foregoing and related ends, theinvention comprises the features hereinafter fully described andparticularly pointed out in the claims. The following description andthe annexed drawings set forth in detail certain illustrativeembodiments of the invention. These embodiments are indicative, however,of but a few of the various ways in which the principles of theinvention may be employed. Other objects, advantages and novel featuresof the invention will become apparent from the following detaileddescription of the invention when considered in conjunction with thedrawings.

BRIEF DESCRIPTION OF THE DRAWINGS

[0024] FIGS. 1A-1D are diagrammatic cross-sections of a portion of asemiconductor structure, illustrating several steps of a methodaccording to one aspect of the invention.

[0025] FIGS. 2A-2F are diagrammatic cross-sections of a portion of asemiconductor structure, illustrating several steps of a methodaccording to another aspect of the invention.

[0026] FIGS. 3A-3F are diagrammatic cross-sections of a portion of asemiconductor structure, illustrating several steps of a methodaccording to a further aspect of the invention.

[0027] FIGS. 4A-4H are diagrammatic cross-sections of a portion of asemiconductor structure, illustrating several steps of a specificexample of a method according to a the invention.

[0028] FIGS. 5A-5J are diagrammatic cross-sections of a portion of asemiconductor structure, illustrating several steps of another specificexample of a method according to the invention.

[0029] FIGS. 6A-6I are diagrammatic cross-sections of a portion of asemiconductor structure, illustrating several steps of a methodaccording to another aspect of the invention.

[0030] FIGS. 7A-7H are diagrammatic cross-sections of a portion of asemiconductor structure, illustrating several steps of a methodaccording to another aspect of the invention.

[0031] FIGS. 8A-8G are diagrammatic cross-sections of a portion of asemiconductor structure, illustrating several steps of a methodaccording to another aspect of the invention.

[0032] FIGS. 9A-9L are diagrammatic cross-sections of a portion of asemiconductor structure, illustrating several steps of another specificexample of a method according to the invention.

[0033]FIGS. 10A and 10B depict two exemplary multi-level air gapstructures according to present invention.

DETAILED DESCRIPTION OF THE INVENTION

[0034] Referring now in detail to the drawings, the various steps of amethod of producing a structure according to one aspect of the inventionare diagrammatically illustrated in FIGS. 1A-1D. In FIGS. 1A and 1B, apatterned layer of sacrificial material 20 is formed on a substrate 22by any suitable technique. This may be accomplished, for example, byfirst forming a layer of the sacrificial material 20 on the substrate 22as depicted in FIG. 1A and then patterning the layer, for example byetching or any other suitable technique, to form the patterned layer ofsacrificial material 20 having one or more “hills” formed by thesacrificial material on the substrate with “valleys” formed between anytwo relatively adjacent hills. A second solid layer of a non-sacrificialmaterial 24 is then formed on the patterned layer in overlying relationto the patterned layer 20 as depicted in FIG. 1C. Then, heat is appliedto the decompose the sacrificial material into one or more gaseousdecomposition products, and one or more of these decomposition productsare removed by passing through the second layer 24. This provides anair-gap structure 28 having one or more air gaps 26 in the closedinterior space or spaces previously occupied by the sacrificial material20.

[0035] Generally, an air-gap structure is formed by using two dielectricmaterials, a sacrificial material which decomposes to gaseous productsand a permanent material (at least permanent for purposes of forming theinterior air gap or gaps) which forms a cover or overcoat through whichone or more of the gaseous products can pass. In one embodiment, suchpassage is by diffusion of one or more of the decomposition productsthrough the overcoat material. Reference herein is made to passage ofthe decomposition products of the sacrificial layer through thepermanent layer. This broadly is intended to encompass passage in anymanner, including though holes or passages in the permanent layer thatmay later be closed. However, in one embodiment, passage is by diffusionthrough a solid permanent layer.

[0036] In one embodiment, the decomposition reaction of the sacrificialmaterial is induced solely by high temperature although other means maybe used. The decomposition temperature should be compatible with thevarious components of the structure so as not to destroy the integritythereof aside from the removal of the sacrificial material to form theair gap or gaps. Typically, such temperature should be less than about500° C. for electrical interconnect devices. In another embodiment, sucha temperature is less than about 450° C. It is contemplated that, in oneembodiment, the decomposition temperature will fall in the range ofabout 380° C. to about 450° C., although materials having decompositiontemperatures as low as about 150° C. may be beneficial. The sacrificialmaterial, however, should be sufficiently thermally stable so that thepermanent material can be processed to a condition where it iselectrically and/or mechanically stable.

[0037] It should be further noted that any one or more of the hereindescribed layers may be composed of multiple sub-layers, as may desiredfor different fabricating techniques. For example, the layer 24 in FIG.1C may be composed of a first sub-layer at the same level as thesacrificial layer and a second sub-layer overlying the first sub-layerand the sacrificial material. Also, the indication that a layer isapplied to an underlying layer does is not intended to preclude thepresence of an intermediate layer that might be employed, for example,to enable bonding of one layer to another.

[0038] In one embodiment, the sacrificial material for carrying out theabove-described method is selected from the cycloolefin class ofcompounds. In another embodiment, the sacrificial material is abicycloolefin. In still another embodiment, the sacrificial material isa norbornene polymer. By norbornene polymer is meant polycyclic additionhomopolymers and copolymers comprising repeating units set forth underFormulae I, II and III below. Copolymers useful in practicing theinvention can include repeating units selected from the group comprisingand/or consisting of Formulae I, II and III, or combinations thereof. Aswould be appreciated by one of ordinary skill in the art, the abovedefinition includes therein those norbornene polymers which arefunctionally equivalent to the polymers set forth in Formulae I, II andIII. One such type of norbornene polymer that is useful as thesacrificial material in the present invention is sold under the Avatrel®trademark by The BF Goodrich Company, Akron, Ohio. The polymer comprisessilyl substituted repeating units represented by the structure set forthunder Formula I below.

[0039] wherein R¹ and R⁴ independently represent hydrogen; linear orbranched (C₁ to C₂₀) alkyl; R² and R³ independently represent hydrogen,linear or branched (C₁ to C₂₀) alkyl or the group:

[0040] R⁹ independently is hydrogen, methyl, or ethyl; R¹⁰, R¹¹′, andR¹² independently represent linear or branched (C_(1 to C) ₂₀) alkyl,linear or branched (C_(1 to C) ₂₀) alkoxy, linear or branched(C_(1 to C) ₂₀) alkyl carbonyloxy (e.g., acetoxy), and substituted orunsubstituted (C₆ to C₂₀) aryloxy; m is a number from 0 to 4; and n is anumber from 0 to 5. In Formula I at least one of substituents R² and R³must be selected from the silyl group represented by the formula setforth under Ia.

[0041] In one embodiment, at least one of R¹⁰, R¹¹, or R¹² is selectedfrom a linear or branched (C₁ to C₁₀) alkoxy group and R⁹ is hydrogen.In another embodiment, each of R¹⁰, R¹¹, and R¹² are the same and areselected from methoxy, ethoxy, propoxy, butoxy, and pentoxy. In yetanother embodiment, n is 0 and R¹⁰, R¹¹, and R¹² are each ethoxy groups,e.g., R² and/or R³ is a triethoxysilyl substituent. When n is 0, it isevident that the silyl functionality is connected directly to thepolycyclic ring through a silicon-carbon bond wherein the carbon atom ofsaid silicon-carbon bond is supplied by a carbon atom on the polycyclicring (i.e., a ring carbon atom).

[0042] In Formula I above, m is, in one embodiment, 0 or 1 asrepresented by structures Ib and Ic, respectively, below:

[0043] wherein R¹ to R⁴ are as previously defined and at least one of R²and R³ must be a silyl substituent represented by Ia. In one embodiment,repeating units where m is 0, i.e., repeating units of structure Ib, areutilized.

[0044] In Formulae I, Ib, and Ic R¹ and R⁴ can taken together with thetwo ring carbon atoms to which they are attached to represent asaturated cyclic group of 4 to 8 carbon atoms. When R¹ and R⁴ are takentogether to form a saturated cyclic group, the cyclic group issubstituted by R² and R³ at least one of which must be a silyl grouprepresented by Ia. Generically such monomers are represented by thefollowing structure:

[0045] wherein B is a methylene (i.e., —CH₂—) group and q is a numberfrom 2 to 6. It should be apparent that when the methylene grouprepresented by B contains an R² or R³ substituent, one of the hydrogenatoms of the —CH₂— group is replaced by the R² or R³ substituent.Representative repeating unit structures are set forth below:

[0046] wherein R², R³, and m are as previously defined.

[0047] Illustrative examples of monomers of Formula I include5-triethoxysilyl-norbornene, 5-trimethylsilyl norbornene,5-trimethoxysilyl norbornene, 5-methyldimethoxysilyl norbornene,5-dimethylmethoxy norbornene.

[0048] In another embodiment of the present invention, the sacrificialpolymer comprises hydrocarbyl substituted polycyclic repeating unitsselected from units represented by Formula II below:

[0049] wherein R⁵, R⁶, R⁷, and R⁸ independently represent hydrogen,linear and branched (C₁ to C₂₀) alkyl, hydrocarbyl substituted andunsubstituted (C₅ to C₁₂) cycloalkyl, hydrocarbyl substituted andunsubstituted (C₆ to C₄₀) aryl, hydrocarbyl substituted andunsubstituted (C₇ to C₁₅) aralkyl, (C₃ to C₂₀) alkynyl, linear andbranched (C₃ to C₂₀) alkenyl, or vinyl; any of R⁵ and R⁶ or R⁷ and R⁸can be taken together to form a (C₁ to C₁₀) alkylidenyl group, R⁵ and R⁸when taken with the two ring carbon atoms to which they are attached canrepresent saturated and unsaturated cyclic groups containing 4 to 12carbon atoms or an aromatic ring containing 6 to 17 carbon atoms; and pis 0, 1, 2, 3, or 4. The hydrocarbyl substituents on the foregoingsubstituents are composed solely of carbon and hydrogen atoms, such as,for example, branched and unbranched (C₁ to C₁₀) alkyl, branched andunbranched (C₂ to C₁₀) alkenyl, and (C₆ to C₂₀) aryl.

[0050] Illustrative examples of hydrocarbyl substituted monomersinclude, but are not limited to, 2-norbornene, 5-methyl-2-norbornene,5-hexyl-2-norbornene, 5-cyclohexyl-2-norbornene,5-cyclohexenyl-2-norbornene, 5-butyl-2-norbornene, 5-ethyl-2-norbornene,5-decyl-2-norbornene, 5-phenyl-2-norbornene, 5-naphthyl-2-norbornene5-ethylidene-2-norbornene, vinylnorbornene, dicyclopentadiene,dihydrodicyclopentadiene, tetracyclododecene, methyltetracyclododecene,tetracyclododecadiene, dimethyltetracyclododecene,ethyltetracyclododecene, ethylidenyl tetracyclododecene,phenyltetra-cyclododecene, trimers of cyclopentadiene (e.g., symmetricaland asymmetrical trimers). In one embodiment, the hydrocarbyl repeatingunit is derived from 2-norbornene.

[0051] In another embodiment of the invention, a sacrificial polymeruseful in carrying out the invention comprises repeating unitsrepresented by Formula III below:

[0052] wherein R⁹ to R¹² independently represent a polar substituentselected from the group: -(A)_(n)—C(O)OR″, -(A)_(n)—OR″,-(A)_(n)—OC(O)R″, -(A)_(n)—OC(O)OR″, -(A)_(n)—C(O)R″,-(A)_(n)—OC(O)C(O)OR″, -(A)_(n)—O-A′-C(O)OR″, -(A)_(n)—OC(O)-A′-C(O)OR″,-(A)_(n)—C(O)O-A′-C(O)OR″, -(A)_(n)—C(O)-A′-OR″,-(A)_(n)—C(O)O-A′-OC(O)OR″, -(A)_(n)—C(O)O-A′-O-A′-C(O)OR″,-(A)_(n)—C(O)O-A′-OC(O)C(O)OR″, -(A)_(n)—C(R″)₂CH(R″)(C(O)OR″), and-(A)_(n)—C(R″)₂CH(C(O)OR″)₂; and p is 0, 1, 2, 3, 4, or 5. The moietiesA and A′ independently represent a divalent bridging or spacer groupselected from divalent hydrocarbon groups, divalent cyclic hydrocarbongroups, divalent oxygen containing groups, and divalent cyclic ethersand cyclic diethers, and n is an integer 0 or 1. When n is 0 it shouldbe apparent that A and A′ represent a single covalent bond. By divalentis meant that a free valence at each terminal end of the group areattached to two distinct groups. The divalent hydrocarbon groups can berepresented by the formula —(C_(d)H_(2d))— where d represents the numberof carbon atoms in the alkylene chain and is an integer from 1 to 10. Inone embodiment, the divalent hydrocarbon groups are selected from linearand branched (C₁ to C₁₀) alkylene such as methylene, ethylene,propylene, butylene, pentylene, hexylene, heptylene, octylene, nonylene,and decylene. When branched alkylene groups are contemplated, it is tobe understood that a hydrogen atom in the linear alkylene chain isreplaced with a linear or branched (C₁ to C₅) alkyl group.

[0053] The divalent cyclic hydrocarbon groups include substituted andunsubstituted (C₃ to C₈) cycloaliphatic moieties represented by theformula:

[0054] wherein a is an integer from 2 to 7 and R^(q) when presentrepresents linear and branched (C₁ to C₁₀) alkyl groups. Divalentcycloalkylene groups include, but are not limited to, cyclopentylene andcyclohexylene moieties represented by the following structures:

[0055] wherein R^(q) is defined above. As illustrated here andthroughout this specification, it is to be understood that the bondlines projecting from the cyclic structures and/or formulae representthe divalent nature of the moiety and indicate the points at which thecarbocyclic atoms are bonded to the adjacent molecular moieties definedin the respective formulae. As is conventional in the art, the diagonalbond line projecting from the center of the cyclic structure indicatesthat the bond is optionally connected to any one of the carbocyclicatoms in the ring. It is also to be understood that the carbocyclic atomto which the bond line is connected will accommodate one less hydrogenatom to satisfy the valence requirement of carbon.

[0056] Exemplary divalent cyclic ethers and diethers are represented by,but not limited to, the structures:

[0057] The divalent oxygen containing groups include (C₂ to C₁₀)alkylene ethers and polyethers. By (C₂ to C₁₀) alkylene ether is meantthat the total number of carbon atoms in the divalent ether moiety mustat least be 2 and can not exceed 10. The divalent alkylene ethers arerepresented by the formula -alkylene-O-alkylene- wherein each of thealkylene groups that are bonded to the oxygen atom can be the same ordifferent and are selected from methylene, ethylene, propylene,butylene, pentylene, hexylene, heptylene, octylene, and nonylene. Thesimplest divalent alkylene ether of the series is the group —CH₂—O—CH₂—.Polyether moieties include, but are not limited to, divalent groups ofthe formula:

—CH₂(CH₂)_(x)O_(y)

[0058] wherein x is an integer from 0 to 5 and y is an integer from 2 to50 with the proviso that the terminal oxygen atom on the polyetherspacer moiety can not be directly linked to a terminal oxygen atom on anadjacent group to form a peroxide linkage. In other words, peroxidelinkages (i.e., —O—O—) are not contemplated when polyether spacers arelinked to any of the terminal oxygen containing substituent groups setforth under R⁹ to R¹² above.

[0059] R⁹ to R¹² can also independently represent hydrogen, linear andbranched (C₁ to C₁₀) alkyl, so long as at least one of the remaining R⁹to R¹² substituents is selected from one of the polar groups representedabove. As is noted with regard to Formula III, p is an integer from 0 to5 (in one embodiment 0 or 1, in another embodiment 0). R″ independentlyrepresents hydrogen, linear and branched (C₁ to C₁₀) alkyl (e.g.,—C(CH₃)), —Si(CH₃), —CH(RP)OCH₂CH₃, —CH(RP)OC(CH₃)₃, linear and branched(C_(1 to C) ₁₀) alkoxyalkylene, polyethers, monocyclic and polycyclic(C₄ to C₂₀) cycloaliphatic moieties, cyclic ethers, cyclic ketones, andcyclic esters (lactones). By (C₁ to C₁₀) alkoxyalkylene is meant that aterminal alkyl group is linked through an ether oxygen atom to analkylene moiety. The group is a hydrocarbon based ether moiety that canbe generically represented as -alkylene-O-alkyl wherein the alkylene andalkyl groups independently contain 1 to 10 carbon atoms each of whichcan be linear or branched. The polyether group can be represented by theformula:

CH₂(CH₂)_(x)OR^(a)

[0060] wherein x is an integer from 0 to 5, y is an integer from 2 to 50and R^(a) represents hydrogen or linear and branched (C₁ to C₁₀) alkyl.Polyether groups include, but are not limited to, poly(ethylene oxide)and poly(propylene oxide). Examples of monocyclic cycloaliphaticmonocyclic moieties include cyclopropyl, cyclobutyl, cyclopentyl,cyclohexyl, dicyclopropylmethyl (Dcmp) and dimethylcyclopropylmethyl(Dmcp), and the like. Examples of cycloaliphatic polycyclic moietiesinclude, but are not limited to, norbornyl, adamantyl,tetrahydrodicyclopentadienyl (tricyclo[5.2.1.0^(2,6)] decanyl), and thelike. Examples of cyclic ethers include, but are not limited to,tetrahydrofuranyl and tetrahydropyranyl moieties. An example of a cyclicketone is a 3-oxocyclohexanonyl moiety. An example of a cyclic ester orlactone is a mevalonic lactonyl moiety. Structures for representativecyclic groups set forth above include:

[0061] wherein R^(p) in the above formulae and cyclic groups representshydrogen or a linear or branched (C₁ to C₅) alkyl group. The Dcpm andDmcp substituents are represented, respectively, as follows:

[0062] In one embodiment, the sacrificial polymers useful in practicingthe present invention encompass homopolymers and copolymers containingrandom repeating units derived from a monomer unit or monomer unitsrepresented by Formula I, or homopolymers or copolymers containingrandom repeating units derived from monomer unit or units represented byFormula II, homopolymers or copolymers containing repeating unitsderived from a monomer unit(s) represented by Formula III and copolymerscomprising a combination of repeating units represented by Formulae Iand II, Formulae I and III, Formulae II and III or Formulae I, II andIII.

[0063] In one embodiment, the sacrificial polymers according to thepresent invention can contain from about 0.1 to 100 mole percent ofsilyl functional polycyclic repeating units, with the remainder of thepolymer comprising repeating units described under Formula II and/orFormula III. In another embodiment, the sacrificial polymers accordingto the present invention can contain from about 1 to 50 mole percent,with the remainder of the polymer comprising repeating units describedunder Formula II and/or Formula III. In yet another embodiment, thesacrificial polymers according to the present invention can contain fromabout 3 to 25 mole percent, with the remainder of the polymer comprisingrepeating units described under Formula II and/or Formula III. In yetanother embodiment, the sacrificial polymers according to the presentinvention can contain from about 5 to 20 mole percent, with theremainder of the polymer comprising repeating units described underFormula II and/or Formula III. In yet another embodiment, thesacrificial polymer comprises repeating units polymerized fromnorbornene and triethoxysilyl-norbornene in a mole percent ratio of80/20 norbornene/triethoxysilylnorbonene.

[0064] The sacrificial polymers according to present invention can beaddition polymers comprising polycyclic repeating units that areconnected to one another via 2,3-linkages that are formed across thedouble bond contained in the norbornene moiety of the prepolymerizedpolycyclic monomer.

[0065] The polymers may be polymerized from appropriately functionalizednorbornene monomers in the presence of a single or multi-component GroupVIII transition metal catalyst system as described in InternationalPatent Application Publication No. WO 97/20871 to The BF GoodrichCompany, published on Jun. 12, 1997, which is hereby incorporated hereinby reference in its entirety.

[0066] The polynorbornene polymers are useful because they have a high(>350° C.) and sufficient thermal stability to accommodate a number ofcommonly employed and other semiconductor manufacturing steps such asplasma enhanced chemical vapor deposition (PECVD) of SiO₂ and lowtemperature copper annealing, and has a decomposition temperature closeto its T_(g), thereby limiting movement which might damage thesemiconductor device.

[0067] In another embodiment, the sacrificial polymer is a polycarbonatepolymer containing repeating units according to the following generalformula of:

[0068] where R represents linear and branched (C₁ to C₂₀) alkyl,hydrocarbyl substituted and unsubstituted (C₁ to C₁₂) cycloalkyl,hydrocarbyl substituted and unsubstituted (C₆ to C₄₀) aryl, hydrocarbylsubstituted and unsubstituted (C₇ to C₁₅) aralkyl, (C₃ to C₂₀) alkynyl,linear and branched (C₃ to C₂₀) alkenyl and n is equal to 2 to about100,000. In another embodiment, n is equal to 2 to about 10,000. In yetanother embodiment, n is equal to 2 to about 1,000.

[0069] In another embodiment, the sacrificial polymer is a polyesterpolymer containing repeating units according to the following generalformula of:

[0070] where R represents linear and branched (C₁ to C₂₀) alkyl,hydrocarbyl substituted and unsubstituted (C₅ to C₁₂) cycloalkyl,hydrocarbyl substituted and unsubstituted (C₆ to C₄₀) aryl, hydrocarbylsubstituted and unsubstituted (C₇ to C₁₅) aralkyl, (C₃ to C₂₀) alkynyl,linear and branched (C₃ to C₂₀) alkenyl; x is an integer from 1 to about20; and n is equal to 2 to about 100,000. In another embodiment, x is aninteger from 1 to about 10 and n is equal to 2 to about 10,000. In yetanother embodiment, x is an integer from 1 to about 6 and n is equal to2 to about 1,000.

[0071] In another embodiment, the sacrificial polymer is a polyetherpolymer containing repeating units according to the following generalformula of:

[0072] where R²⁰ and R²¹ independently represent linear and branched (C₁to C₂₀) alkyl, hydrocarbyl substituted and unsubstituted (C₅ to C₁₂)cycloalkyl, hydrocarbyl substituted and unsubstituted (C₆ to C₄₀) aryl,hydrocarbyl substituted and unsubstituted (C₇ to C₁₅) aralkyl, (C₃ toC₂₀) alkynyl, linear and branched (C₃ to C₂₀) alkenyl and n is equal to2 to about 100,000. In another embodiment, n is equal to 2 to about10,000. In yet another embodiment, n is equal to 2 to about 1,000.

[0073] Such polycarbonates, polyesters and polyethers can be used assacrificial materials in the present invention because they can bepatterned on a device by an appropriate physical or chemical method. Forexample, reactive ion etching can be used to provide a patterned surfaceof a polycarbonate polymer. Additionally, laser ablation, wet etching,direct printing, hot embossing, screen printing, pattern printing, andphotolithography can be utilized to create or produce a patterned layerof one or more of the above-mentioned sacrificial materials.

[0074] In one embodiment, the polycarbonate sacrificial polymer of thepresent invention is selected from polyethylene carbonate (PEC) andpolyproplyene carbonate.

[0075] In another embodiment, the sacrificial polymer of the presentinvention can be a methacrylate or acrylate polymer. In one embodiment,the methacrylate polymer is a polymethyl methacrylate polymer.

[0076] In one embodiment, the methacrylate or acrylate polymer of thepresent invention has a molecular weight of about 1,000 to about1,000,000. In another embodiment, the methacrylate or acrylate polymerof the present invention has a molecular weight of about 10,000 to about500,000. In another embodiment, the methacrylate or acrylate polymer ofthe present invention has a molecular weight of about 100,000 to about250,000.

[0077] In another embodiment, the sacrificial polymer utilized inpracticing this invention is a negative or positive photo-sensitivesacrificial material. The photo-sensitive property of such a polymer caneither be inherent in the sacrificial material utilized or can beconferred thereto by the addition of one or more photo-sensitivematerials.

[0078] It is believed that the sacrificial polymers utilized inpracticing this invention are suited as sacrificial materials insemiconductor device manufacturing because the material thermallydecomposes close to its T_(g). In other words, the polymer remainsmechanically stable until the decomposition temperature is reachedenabling the polymer to endure the rather harsh processing steps (e.g.,repeated heat cycles) during semiconductor manufacture. The disadvantagewith the prior art polymers is that their T_(g)'s are well below theirdecomposition temperatures, leading to mechanical failure before thedecomposition temperature is reached.

[0079] With regard to the polycycloolefinic sacrificial polymermaterials, it has been found that by incorporating polycycloolefinicrepeating units that contain pendant hydrocarbyl (Formula II) and/orpendant polar (Formula II) substituents into the sacrificial polymerbackbone the decomposition temperatures of the silyl substitutedpolycycloolefinic polymer can be significantly lowered. Thedecomposition temperature of polymers containing 80/20 mole percent ofnorbornene/triethoxysilylnorbonene (approximately 430° C.) can belowered by approximately 30° C. by replacing the norbornene repeatingunits in the copolymer with repeating units containing pendant linearand/or branched (C₁ to C₂₀) alkyl substituents. For example, the thermaldecomposition temperature for a copolymer containingbutylnorbornene/triethoxysilylnorbornene in a mole percent ratio of 95/5is lowered to 405° C. We expect that the decomposition temperature ofthe copolymer can be lowered even further (up to approximately 100° C.)by replacing the norbornene repeating units in the copolymer withrepeating units containing the polar substituents described underFormula III. Homopolymers of norbornyl acetate and norbornyl ethylcarbonate have thermal decomposition temperatures of 356° C. and 329°C., respectively. The polar groups include ester, carbonate, and acetatesubstituents and the like. To effect lower decomposition temperatures ofthe silyl substituted polymers, the polymer should contain about 50 molepercent of polycyclic repeating units having pendant hydrocarbyl orpolar functionality. In another embodiment, the polymer should containgreater than 50 mole percent of polycyclic repeating units havingpendant hydrocarbyl or polar functionality. In yet another embodiment,the polymer should contain about 51 to about 99 mole percent ofpolycyclic repeating units having pendant hydrocarbyl or polarfunctionality. In still another embodiment, the polymer should containabout 65 to about 80 mole percent of polycyclic repeating units havingpendant hydrocarbyl or polar functionality.

[0080] The aforesaid sacrificial polymers can be heated to above theirdecomposition temperature, typically in the range of about 380° C. toabout 450° C., to cause the polymers to decompose into theirdecomposition products which can diffuse through various materials usedto form semiconductor devices including air gaps. The materials includepolymer dielectrics such as silicon dioxide, silicon nitride, siliconoxynitride, polyarylene ether, spin-on-glasses (e.g.,methylsilsesquioxane (MSQ), hydrogen-silsesquioxane (HSQ), or a mixedsilsesquioxane), and polyimides, for example, Olin-Ciba Geigy (OCG)Probimide® 293 and 412, Amoco Ultradel® 7501 and DuPont Pyralin® 2545,2611, or 2731. In one embodiment, the dielectric polymer used in thepresent invention is photosensitive.

[0081] The forgoing methodology can be applied to form air gaps in avariety of electrical devices and particularly in relation to electricalinterconnects in integrated circuits and other electronic packages. Theair gaps may be used on opposite sides of a conductive member or membersin both interplanar and intraplanar arrangements to provide a lowdielectric insulator with dielectric constants generally less than about2. In another embodiment, the dielectric constants can be less thanabout 1.5. In yet another embodiment, the dielectric constants can beless than about 1.25. In still another embodiment, the dielectricconstants can be less than about 1.0. The lower the capacitance, thefaster the electrical signal can be transmitted through the conductorsand the lower the crosstalk between conductors.

[0082] The above-mentioned sacrificial polymers are advantageous becausegenerally they leave little or essentially no residue. However, someresidue may be desirable. For example, a thin film of SiO₂ (or TiO₂ ifTi is used in place of Si in the functionalized norbornene) may be leftto insulate the electrical conductors or control corrosion. Actual testshave shown about 100 Å of residue when 5 μm of material are decomposed.

[0083] FIGS. 2A-2F illustrate one possible method of forming an air gapor region between two conductive regions or elements, such as metallines, according to the present invention. In FIGS. 2A and 2B, apatterned layer of sacrificial material 30 is formed on a substrate 32.The substrate 32 may have patterns already on it, or it may be anunpatterned material. The substrate may be a base layer or a layer ofmaterial overlying a base layer such as an insulating layer of SiO₂ thatmay overlie the devices on an integrated circuit chip (not shown). Byway of specific example, the substrate may be a semiconductor waferwhich may, for example, contain transistors, diodes, and othersemiconductor elements (as are well known in the art).

[0084] As depicted in FIG. 2A, a uniform layer of the sacrificialmaterial 30 is deposited on the substrate 32. This may be done in anysuitable manner, for example, by spin coating, spraying, meniscus,extrusion or other coating methods, by pressing or laying a dry filmlaminate onto the substrate, etc.

[0085] In FIG. 2B, the layer of sacrificial material is patterned toproduce the patterned layer of the sacrificial material 30, the patternof which corresponds to the desired pattern of one or more air gaps tobe formed in the semiconductor device. Any suitable technique can beused to pattern the layer of sacrificial material, including, forexample, laser ablating, etching, etc. The sacrificial material may beof a type that is or may be made photosensitive to facilitatepatterning.

[0086] In FIG. 2C, a layer of conductive material 34, (in oneembodiment, the conductive material is a metal) is deposited over thepatterned layer of sacrificial material 30. This may be done by anysuitable technique including, for example, metal sputtering, chemicalvapor deposition (CVD), physical vapor deposition (PVD), electroplating,electroless plating, etc.

[0087] In FIG. 2D, the metal layer 34 is planarized as needed by anysuitable technique including, for example, chemical-mechanical polishing(CMP). If CMP is used with the above-described polynorbornene polymer,and other polymers as well, a layer of silicon dioxide can be applied tothe surface of the sacrificial layer to provide an etch stop.

[0088] In FIG. 2E, a permanent dielectric 36 is deposited over thepatterned layer of sacrificial material 30 with the metal inlay 34. Thepermanent dielectric 36 is deposited as a solid layer and covers thesacrificial layer 30 and at least the tops of the metal leads 34. Thepermanent dielectric layer may be planarized before or after removal ofthe sacrificial material. The permanent dielectric layer, for example,may be silicon dioxide, polyimide or other material. The permanentdielectric layer may be deposited by spin coating, spray coating ormeniscus coating (typically using the sacrificial material dissolved ina solvent), chemical vapor deposition, plasma enhanced chemical vapordeposition, sol-gel process, or other method. As seen in FIG. 2E, themetal layer can be conveniently formed with a height less than theheight of the adjacent sacrificial material. As will be appreciated,this will result in air gaps that extend above the tops of the metalleads, as is desirable to reduce capacitive coupling. Also, thesubstrate could have trenches formed therein in a pattern correspondingto the pattern of the sacrificial material, so that the resultant airgaps will extend below the metal leads located on lands on the substratebetween the trenches.

[0089] The sacrificial material 30 is removed through the permanentdielectric layer 36 to form the air gaps 38 as shown in FIG. 2F. Theremoval of the sacrificial material is, in one embodiment, accomplishedby thermal decomposition and passage of one or more of the decompositionproducts through the permanent dielectric layer 36 by diffusion. Asabove indicated, the sacrificial materials of the present invention willundergo thermal decomposition at temperatures on the order of about 450°C., and lower, with essentially no residue being left in the air gaps ofthe resultant semiconductor structure 40. Also, the decompositionproducts are diffusable through many dielectric materials useful formingthe permanent dielectric layer, including polyimides.

[0090] The rate of decomposition should be slow enough so that diffusionthrough the permanent dielectric will occur. Diffusion typically arisesfrom a pressure buildup within the air gap. This pressure build upshould not be so great as to exceed the mechanical strength of thepermanent dielectric. Increased temperature will generally aid diffusionas diffusivity of gas though the permanent dielectric will normallyincrease with temperature. In one embodiment, the sacrificial materialis decomposed at a relatively slow rate. In one embodiment, the heatingrate is between about 0.5 to about 10° C./minute. In another embodiment,the heating rate is between about 1 to about 5° C./minute. In yetanother embodiment, the heating rate is between about 2 to about 3°C./minute.

[0091] As will be appreciated, the air gaps may contain residual gasalthough generally the residual gas will eventually exchange with air.However, steps may be taken to prevent such exchange, or dispose adifferent gas (a noble or inert gas for example) or a vacuum in the airgaps. For example, the semiconductor structure may be subjected tovacuum conditions to extract any residual gas from the air gaps bydiffusion or other passage through the overcoat layer 24 or otherwise,after which the semiconductor structure may be coated by a suitablesealing material blocking any further passage of gases through theovercoat layer. Before the semiconductor structure is sealed, it may besubjected to a controlled gas atmosphere, such as one containing aninert gas (e.g., nitrogen), to fill the air gaps with such gas.

[0092] In another embodiment, the semiconductor structure can besubjected to the necessary decomposition temperature while contained inan atmosphere which will enable exchange or absorption of one or morereactive molecules into the air gaps formed during decomposition. Forexample, the semiconductor device can be subjected to decomposition inan oxygen atmosphere or a SiH₄. An oxygen atmosphere will, for example,yield hydrophilic air gaps.

[0093] As will be appreciated, further processing steps may be performedon the semiconductor structure 40, for example to form additional layerof interconnection in the semiconductor device.

[0094] Those skilled in the art will also appreciate that othertechniques may be employed to remove the sacrificial material, althoughless desirable and/or dictated by the type of sacrificial materialutilized. The sacrificial material could be a photoresist that willdecompose in oxygen (or more generally air or some otheroxygen-containing atmosphere, or including an oxygen plasma or ozone).In connection therewith, a permanent layer may comprise, for example, asilica-based xerogel with a 10-90% porosity enabling passage of theoxygen into contact with the photoresist. The oxygen moves through thesilica-based xerogel to reach and react with the photoresist to convertit to a gas that passes out through the silica-based xerogel.

[0095] In FIGS. 3A-3F, a method of forming an air gap or region betweentwo conductive regions or elements, such as metal lines, according toanother aspect of the invention, is diagrammatically illustrated. InFIGS. 3A and 3B, a patterned layer of conductive material 50, such asaluminum, copper, gold, etc., is formed on a substrate 52. Again, thesubstrate may be a base layer or a layer of material overlying a baselayer such as an insulating layer of SiO₂ that may overlie the deviceson an integrated circuit chip (not shown). By way of specific example,the substrate may be a semiconductor wafer which may, for example,contain transistors, diodes, and other semiconductor elements (as arewell known in the art.

[0096] As depicted in FIG. 3A, a uniform layer of the conductivematerial 50 is deposited on the substrate. This may be done in anysuitable manner, for example, by metal sputtering, chemical vapordeposition (CVD), plating (particularly electroless plating) or othermethods. In FIG. 3B, the layer of conductive material 50 is patterned toproduce a pattern of the conductive material corresponding to thedesired pattern of one or more electrical conductors, e.g. metal lines,leads, regions, etc., to be formed in the semiconductor device. Anysuitable technique can be used to pattern the layer of conductivematerial, including, for example, laser ablating, etching, etc.

[0097] In FIG. 3C, a layer of sacrificial material 54 is deposited overthe patterned layer of conductive material 50. This may be done by anysuitable technique including, for example, spin coating, spraying,meniscus, extrusion or other coating methods, by pressing or laying adry film laminate onto the substrate, etc.

[0098] In FIG. 3D, any excess sacrificial material overlying the tops ofthe conductors 50 is removed and the sacrificial layer is planarized, asneeded, by any suitable technique including, for example, CMP, reactiveion etching, etc.

[0099] In FIG. 3E, a permanent dielectric 56 is deposited over thepatterned conductive layer with the sacrificial material inlay. Thepermanent dielectric is deposited as a solid layer and covers thesacrificial layer and at least the tops of the metal leads of theconductive layer.

[0100] Then, like in the manner described above in respect of the methodillustrated in FIGS. 2A-2F, the sacrificial material is removed throughthe permanent dielectric layer to form the air gaps 58 as shown in FIG.3F. Again, in one embodiment, the removal of the sacrificial material isaccomplished by thermal decomposition and passage of one or more of thedecomposition products through the permanent dielectric layer 56 bydiffusion. As above indicated, the sacrificial materials of the presentinvention will undergo thermal decomposition at temperatures on theorder of about 400° C., and lower, with essentially no residue beingleft in the air gaps in the resultant semiconductor structure 60. Also,the decomposition products are diffusable through many dielectricmaterials useful in forming the permanent dielectric layer, includingpolyimides. Also, as above indicated, other techniques may also beemployed to remove the sacrificial material, such as the othertechniques described above.

[0101] Referring now to FIGS. 4A-4H, there is illustrated a specificexample of a method of forming air gaps (tunnels) in an oxide using atleast one of the sacrificial materials discussed in detail above. Thisexemplary specific method involved the steps of:

[0102] 1. In FIG. 4A, a clean, polished silicon wafer 70 is used(although as above indicated many other substrates could be usedincluding ceramic or metal materials).

[0103] 2. In FIG. 4B, a sacrificial material 72 (in this instanceAvatrel® polynorbornene polymer) is spin coated onto the wafer. Spincoating involves rotating the wafer, for example at 1000 to 4000rotations per minute, and dispensing a solution of the sacrificialmaterial and an appropriate solvent in which the sacrificial material isdissolved. The solvent may be mesitylene, although other suitablesolvents may be used such as decalin or other hydrocarbon solvents. Whenpendant polar substituents are present on the sacrificial polymer,propylene glycol monomethyl ether acetate (PGMEA) can be employed as asuitable solvent. The spin coating produces a uniform, thin film on thewafer having a thickness of about 0.2 to about 6 micrometers, with auniformity less than about ±5% across the sample. However, thicker orthinner films could be applied as desired for a given application. Afterthe coating is applied, the wafer is baked in an oven in air at about100° C. to remove the solvent. The polynorbornene polymer is then bakedat about 200 to about 300° C. in nitrogen for one hour to remove thesolvent.

[0104] 3. In FIG. 4C, a layer of plasma enhanced chemical vapordeposited (PECVD) silicon dioxide 74 is deposited on the surface of thepolynorbornene polymer 72 using standard conditions. Suitable gases aresilane and nitrous oxide.

[0105] 4. In FIG. 4D, a photoresist 76 is deposited onto the wafer byspin coating, soft baked, exposed, developed and then hard baked understandard conditions following manufacturer's specifications.

[0106] 5. In FIG. 4E, the sample is reactive ion etched. The pattern inthe photoresist 76 is transferred to the silicon dioxide 74 by firstusing a fluorine containing plasma. The polynorbornene polymer 72 isthen etched by using an oxygen/fluorine plasma. During the process, thephotoresist is also etched. After the polynorbornene polymer is etchedin the exposed areas, a fluorine plasma is used to strip the silicondioxide mask. The sample now has only patterned polynorbornene polymer72 as shown in FIG. 4F.

[0107] 6. In FIG. 4G, silicon dioxide 78 (although other permanentdielectric materials could be used) is deposited onto the patternedpolynorbornene polymer 72. The process is similar to that used in Step 3above to deposit the silicon dioxide on the surface of thepolynorbornene polymer. The polynorbornene polymer is now totallyencapsulated in a permanent dielectric material 78.

[0108] 7. In FIG. 4H, the sample is heated to a temperatures greaterthan the decomposition temperature of the polynorbornene polymer 72. Thesacrificial material decomposes and one or more of the gaseousdecomposition products diffuse out through the overcoat material 78.

[0109] 8. The result is an oxide composite 80 including air gaps 82completely surrounded by dielectric material 78.

[0110] Referring now to FIGS. 5A-5H, there is illustrated a specificexample of a method of forming air gaps between metal lines of anelectrical interconnect device or layer using, for example, apolynorbornene polymer. This exemplary specific method involved thesteps of:

[0111] 1. In FIG. 5A, a clean, polished silicon wafer 90 is used.

[0112] 2. In FIG. 5B, a 1000 Å chromium layer followed by 2000 Å of goldis sputtered onto the wafer 90 to form a composite chromium/gold layer92. The sputtering may use direct current (DC) sputtering.

[0113] 3-7. In FIGS. 5C-5F, a layer of a sacrificial material 94 (inthis instance the sacrificial material is a polynorbornene polymer) isapplied and patterned using silicon dioxide 96 and photoresist 98 asdescribed above in Steps 3-7 of the method illustrated in FIGS. 4A-H.

[0114] 8. In FIG. 5G, the sample is similar to the sample at Step 6 ofthe method illustrated in FIGS. 4A-H, except that a Cr/Au layer 92 liesunder the polynorbornene polymer 94.

[0115] 9. In FIG. 5H, gold is plated until its height is the same as theheight of the polynorbornene polymer 94. The Cr/Au layer 92 serves as anelectrical contact and base for the plating of gold between the regionsof polynorbornene polymer 94. The electroplating may be done in aconventional, pH+7.2 potassium gold cyanide bath using a phosphatebuffer.

[0116] 10. In FIG. 51, the gold layer 100 and sacrificial layer 94 arecoated with PECVD silicon dioxide 102, just as in Step 7 of the methodillustrated in FIGS. 4A-H.

[0117] 11. In FIG. 5J, the sample is heated to decompose thepolynorbornene polymer 94 and form one or more air gaps 104 betweenadjacent metal lines 100 in the resultant semiconductor structure 106.

[0118] Referring now to FIGS. 6A-6I, there is illustrated a specificexample of a method of forming multi-layer air gaps in a layer of asolid non-sacrificial material. This exemplary specific method involvedthe steps of:

[0119] 1. In FIGS. 6A and 6B, a patterned layer of sacrificial material110 is formed on a substrate 112 by any suitable technique. This may beaccomplished, for example, by first forming a layer of the sacrificialmaterial on the substrate 112 as depicted in FIG. 6A and then patterningthe layer, for example by etching or any other suitable technique, toform the patterned layer of sacrificial material 110 having one or more“hills” formed by the sacrificial material on the substrate with“valleys” formed between any two relatively adjacent hills.

[0120] 2. In FIG. 6C, a second solid layer of a non-sacrificial material114 is then formed on the patterned layer in overlying relation to thepatterned layer 110.

[0121] 3. In FIG. 6D, the sample is heated to a temperature sufficientto decompose the sacrificial material 110 thereby forming air gaps 116.The sacrificial material decomposes and one or more of the gaseousdecomposition products diffuse out through the second solid layer of anon-sacrificial material 114.

[0122] 4. In FIGS. 6E and 6F a second patterned layer of sacrificialmaterial 118 is formed on the second solid layer of a non-sacrificialmaterial 114 by any suitable technique. This may be accomplished, forexample, by first forming the second layer of the sacrificial material118 on the second solid layer of a non-sacrificial material 114 asdepicted in FIG. 6F and then patterning the second layer, for example byetching or any other suitable technique, to form the second patternedlayer of sacrificial material 118 having one or more “hills” formed bythe sacrificial material on the substrate with “valleys” formed betweenany two relatively adjacent hills.

[0123] 5. In FIG. 6G, a third solid layer of a non-sacrificial material120 is then formed on the second patterned layer in overlying relationto the second patterned layer 118 (the composition of this layer can beidentical to or different from layer 114).

[0124] 6. In FIG. 6H, the sample is heated to a temperature sufficientto decompose the sacrificial material 118 thereby forming air gaps 122.The sacrificial material decomposes and one or more of the gaseousdecomposition products diffuse out through the second solid layer of anon-sacrificial material 120.

[0125] 7. The result is an air-gap structure 124 a having two or morelevels of air gaps 116 and 122 in the closed interior space or spacespreviously occupied by the sacrificial materials 110 and 118. In oneembodiment, as shown in device 132 a, the air gaps 122 can be aligned soas to directly over top of air gaps 116. Alternatively, otherarrangements of the multi levels of air gaps are contemplated by thepresent invention. For example, as is illustrated in device 132 b ofFIG. 6I the air gaps 122 can be formed so as to form a multi level“staggered” arrangement with air gaps 116 thereby yielding air gapstructure 124 b.

[0126] Additionally, it should be noted that a boundary may or may notexist between layers 114 and 120 depending upon the composition of theselayers and the manner in which layer 120 is formed. Also, thesacrificial material used to form the first level of air gaps and thatused to form the second (or any subsequent level of air gaps) can be thesame material or a different material.

[0127] Referring now to FIGS. 7A-7H, there is illustrated a specificexample of a method of simultaneously forming multi-layer air gaps in alayer of a solid non-sacrificial material. This exemplary specificmethod involved the steps of:

[0128] 1. In FIGS. 7A and 7B, a patterned layer of sacrificial material140 is formed on a substrate 142 by any suitable technique. This may beaccomplished, for example, by first forming a layer of the sacrificialmaterial on the substrate 142 as depicted in FIG. 7A and then patterningthe layer, for example by etching or any other suitable technique, toform the patterned layer of sacrificial material 140 having one or more“hills” formed by the sacrificial material on the substrate with“valleys” formed between any two relatively adjacent hills.

[0129] 2. In FIG. 7C, a second solid layer of a non-sacrificial material144 is then formed on the patterned layer in overlying relation to thepatterned layer 140.

[0130] 3. In FIGS. 7D and 7E, a second patterned layer of sacrificialmaterial 146 is formed on the second solid layer of a non-sacrificialmaterial 144 by any suitable technique. This may be accomplished, forexample, by first forming a second layer of the sacrificial material onthe second solid layer of a non-sacrificial material 144 as depicted inFIG. 7D and then patterning the second layer, for example by etching orany other suitable technique, to form the second patterned layer ofsacrificial material 146 having one or more “hills” formed by thesacrificial material on the second solid layer of a non-sacrificialmaterial 144 with “valleys” formed between any two relatively adjacenthills.

[0131] 4. In FIG. 7F, a third solid layer of a non-sacrificial material148 is then formed on the second patterned layer in overlying relationto the second patterned layer 146. The composition of this layer can beidentical to or different from layer 144, and, as noted above, aboundary between layers 144 and 148 may or may not exist.

[0132] 5. In FIG. 7G, the sample is heated to a temperature sufficientto decompose both sacrificial material 140 and 146 thereby forming airgaps 150 and 152, respectively. Both sacrificial materials decompose andone or more of the gaseous decomposition products diffuse out throughthe second and third solid layers of a non-sacrificial material 144 and148, respectively, for sacrificial material 140, and through the thirdsolid layer of a non-sacrificial material 148 for sacrificial material146.

[0133] 7. The result is an air-gap structure 154 a having two or morelevels of air gaps 150 and 152 in the closed interior space or spacespreviously occupied by the sacrificial materials 140 and 146. In oneembodiment, as shown in device 156 a, the air gaps 152 can be aligned soas to directly over top of air gaps 150. Alternatively, otherarrangements of the multi levels of air gaps are contemplated by thepresent invention. For example, as is illustrated in device 156 b ofFIG. 7H the air gaps 152 can be formed so as to form a multi level“staggered” arrangement with air gaps 150 thereby yielding air gapstructure 154 b.

[0134] It should be noted that with regard to the method of FIGS. 6A-6Iand that of FIGS. 7A-7H, the main difference is that in the method ofFIGS. 6A-6I the multi levels of air gaps are formed sequentially and inFIGS. 7A-7H they are formed simultaneously. Numerous considerations playa role in determining which method is most suitable. For example, thecomposition of the non-sacrificial and sacrificial layers, the structuredesired, the mechanical strength of the first level (in the process ofFIGS. 6A-6I the first level has to be of sufficient strength towithstand the processing of the second level), and the ability of thesacrificial material to diffuse through not only one but two or morelayers of non-sacrificial material (see the method of FIGS. 7A-7H).

[0135] FIGS. 8A-8G illustrate one possible method of forming an air gapor region between two conductive regions or elements, such as metallines, in which the conductive regions are over-coated and thus isolatedfrom direct contact with the air gap structures according to the presentinvention. In FIGS. 8A and 8B, a patterned layer of sacrificial material160 is formed on a substrate 162. The substrate 162 may have patternsalready on it, or it may be an unpatterned material. The substrate maybe a base layer or a layer of material overlying a base layer such as aninsulating layer of SiO₂ that may overlie the devices on an integratedcircuit chip (not shown). By way of specific example, the substrate maybe a semiconductor wafer which may, for example, contain transistors,diodes, and other semiconductor elements (as are well known in the art).

[0136] 1. In FIG. 8A, a uniform layer of the sacrificial material 160 isdeposited on the substrate 162. This may be done in any suitable manner,for example, by spin coating, spraying, meniscus, extrusion or othercoating methods, by pressing or laying a dry film laminate onto thesubstrate, etc.

[0137] 2. In FIG. 8B, the layer of sacrificial material is patterned toproduce the patterned layer of the sacrificial material 160, the patternof which corresponds to the desired pattern of one or more air gaps tobe formed in the semiconductor device. Any suitable technique can beused to pattern the layer of sacrificial material, including, forexample, laser ablating, etching, etc. The sacrificial material may beof a type that is or may be made photosensitive to facilitatepatterning.

[0138] 3. In FIG. 8C, a layer of conductive material 164, (in oneembodiment, the conductive material is any suitable metal or alloy orcomposite thereof) is deposited over the patterned layer of sacrificialmaterial 160. This may be done by any suitable technique including, forexample, metal sputtering, chemical vapor deposition (CVD), physicalvapor deposition (PVD), electroplating, electroless plating, etc.

[0139] 4. In FIG. 8D, the conductive layer 164 is removed as needed byany suitable technique including, for example, a wet chemical etchutilizing a suitable etching compound (e.g., nitric acid). If a wetchemical etch is used a layer of silicon dioxide can be applied to thesurface of the sacrificial layer to provide an etch stop. As can be seenfrom FIG. 8D layer 164 is removed not only on its surface but also onthe sides thereof which are either in contact with the patternedsacrificial polymer layer 160 or at the edges of the device.

[0140] 5. In FIG. 8E, a permanent dielectric 166 having excellentgap-fill capabilities (e.g., a polyimide) is deposited over thepatterned layer of sacrificial material 160 with the conductive inlay164. The permanent dielectric 166 is deposited as a solid layer andcovers the sacrificial layer 160 and overcoats at least the tops andsides of the conductive leads 164. The permanent dielectric layer may beplanarized before or after removal of the sacrificial material. Thepermanent dielectric layer, for example, may be silicon dioxide,polyimide or other material. The permanent dielectric layer may bedeposited by spin coating, spray coating or meniscus coating (typicallyusing the sacrificial material dissolved in a solvent), chemical vapordeposition, plasma enhanced chemical vapor deposition, sol-gel process,or other method. As seen in FIG. 8E, the conductive layer can beconveniently formed with a height less than the height of the adjacentsacrificial material. As will be appreciated, this will result in airgaps that extend above the tops of the conductive leads, as is desirableto reduce capacitive coupling. Also, the substrate could have trenchesformed therein in a pattern corresponding to the pattern of thesacrificial material, so that the resultant air gaps will extend belowthe conductive leads located on lands on the substrate between thetrenches.

[0141] 6. In FIG. 8F, the sacrificial material 160 is removed throughthe permanent dielectric layer 166 to form the air gaps 168. The removalof the sacrificial material is, in one embodiment, accomplished bythermal decomposition and passage of one or more of the decompositionproducts through the permanent dielectric layer 166 by diffusion. Asabove indicated, the sacrificial materials of the present invention willundergo thermal decomposition at temperatures on the order of about 450°C., and lower, with essentially no residue being left in the air gaps ofthe resultant semiconductor structure 170 a. Also, the decompositionproducts are diffusable through many dielectric materials useful formingthe permanent dielectric layer, including polyimides.

[0142] Referring specifically to FIG. 8G, FIG. 8G discloses anotherembodiment according to steps 1-6 discussed immediately above with theexception that the conductive layer 164 is planarized in step 4 asneeded by any suitable technique including, for example, a wet chemicaletch utilizing a suitable etching compound (e.g., nitric acid).Additionally, as can be seen from FIG. 8G, the planarization process inthis embodiment is conducted so as to create gaps between adjacentportions of the sacrificial material 160 and the conductive layer 164 byremoving a portion of the conductive layer adjacent to sacrificialmaterial 160. Again, if a wet chemical etch is used a layer of silicondioxide can be applied to the surface of the sacrificial layer toprovide an etch stop. After completion of step 4 the device is furtherprocessed according to steps 5 and 6 as discussed above to yieldsemiconductor structure 170 b.

[0143] Referring now to FIGS. 9A-9L, there is illustrated a specificexample of a method of forming air gaps between conductive lines of anelectrical interconnect device or layer using a sacrificial polymermaterial (in this instance a polynorbornene polymer was utilized). Thisexemplary specific method involved the steps of:

[0144] 1. In FIG. 9A, a clean, polished silicon wafer 180 is used.

[0145] 2. In FIG. 9B, a seed layer of Ti/Cu/Ti is sputtered onto thewafer 180 to form a layer 182. The sputtering may use direct current(DC) sputtering. Layer 92 may be any suitable thickness. For example, inone embodiment, layer 92 is about 10 Å to about 500,000 Å. In anotherembodiment, layer 92 is about 10 Å to about 250,000 Å thick. In yetanother embodiment, layer 92 is about 1000 Å to about 100,00 Å thick.

[0146] 3-7. In FIGS. 9C-9F, a layer of a sacrificial material 184 (inthis instance the sacrificial material is a polynorbornene polymer) isapplied and patterned using silicon dioxide 186 and photoresist 188 asdescribed above in Steps 3-7 of the method illustrated in FIGS. 4A-H.

[0147] 8. In FIG. 9G, the sample is similar to the sample at Step 6 ofthe method illustrated in FIGS. 4A-H, except that a Ti/Cu/Ti layer 182lies under the polynorbornene polymer 184.

[0148] 9. In FIG. 9H, a layer of conductive material 190 (e.g., a metalsuch as copper, aluminum or gold) is deposited over the patterned layerof sacrificial material 184. This may be done by any suitable techniqueincluding, for example, metal sputtering, chemical vapor deposition(CVD), physical vapor deposition (PVD), electroplating, electrolessplating, etc.

[0149] 10. In FIG. 9I, the conductive layer 190 is removed as needed byany suitable technique including, for example, a wet chemical etchutilizing a suitable etching compound (e.g., nitric acid). If a wetchemical etch is used a layer of silicon dioxide can be applied to thesurface of the sacrificial layer to provide an etch stop. As can be seenfrom FIG. 9I layer 190 is removed not only on its surface but also onthe sides thereof which are either in contact with the patternedsacrificial polymer layer 184 or at the edges of the device.

[0150] 11. In FIG. 9J, a permanent dielectric 192 having excellentgap-fill capabilities (e.g., a polyimide) is deposited over thepatterned layer of sacrificial material 184 with the conductive inlay190. The permanent dielectric 1192 is deposited as a solid layer andcovers the sacrificial layer 1184 and overcoats at least the tops andsides of the conductive leads 190. The permanent dielectric layer may beremoved before or after removal of the sacrificial material. Thepermanent dielectric layer, for example, may be silicon dioxide,polyimide or other material. The permanent dielectric layer may bedeposited by spin coating, spray coating or meniscus coating (typicallyusing the sacrificial material dissolved in a solvent), chemical vapordeposition, plasma enhanced chemical vapor deposition, sol-gel process,or other method. As seen in FIG. 9J, the conductive layer can beconveniently formed with a height less than the height of the adjacentsacrificial material. As will be appreciated, this will result in airgaps that extend above the tops of the conductive leads, as is desirableto reduce capacitive coupling. Also, the substrate could have trenchesformed therein in a pattern corresponding to the pattern of thesacrificial material, so that the resultant air gaps will extend belowthe conductive leads located on lands on the substrate between thetrenches.

[0151] 12. In FIG. 9K, the sacrificial material 184 is removed throughthe permanent dielectric layer 192 to form the air gaps 196. The removalof the sacrificial material is, in one embodiment, accomplished bythermal decomposition and passage of one or more of the decompositionproducts through the permanent dielectric layer 192 by diffusion. Asabove indicated, the sacrificial materials of the present invention willundergo thermal decomposition at temperatures on the order of about 450°C., and lower, with essentially no residue being left in the air gaps ofthe resultant semiconductor structure 200 a. Also, the decompositionproducts are diffusable through many dielectric materials useful formingthe permanent dielectric layer, including polyimides.

[0152] Referring specifically to FIG. 9L, FIG. 9L discloses anotherembodiment according to steps 1-12 discussed immediately above with theexception that the conductive layer 190 is planarized in step 10 asneeded by any suitable technique including, for example, a wet chemicaletch utilizing a suitable etching compound (e.g., nitric acid).Additionally, as can be seen from FIG. 9L, the planarization process inthis embodiment is conducted so as to create gaps between adjacentportions of the sacrificial material 184 and the conductive layer 190 byremoving a portion of the conductive layer adjacent to sacrificialmaterial 184. Again, if a wet chemical etch is used a layer of silicondioxide can be applied to the surface of the sacrificial layer toprovide an etch stop. After completion of step 10 the device is furtherprocessed according to steps 11 and 12 as discussed above to yieldsemiconductor structure 200 b.

[0153] Alternative air-gap structures may use various ways of formingthe metal pattern so that it is not shorted together. First, electrolessplating of metal may replace the electroplating of metal. Second, themetal pattern may be first formed on the silicon wafer (plated to itsfull height), and then the sacrificial material may be deposited. Thesacrificial material covering the metal pattern then may be removedbefore the permanent dielectric is deposited, as by chemical mechanicalpolishing, or other techniques.

[0154]FIGS. 10A and 10B depict two possible multi-level air gaparrangements. It should be noted that the present invention is notlimited to just these two arrangements. As can be seen from FIG. 10A, amulti-level air gap structure can be produced whereby two air gaps areformed on either side vertically of, for example, a conductive line.FIG. 10B depicts a multi-level staggered arrangement. As discussedabove, the present invention is not limited to just these arrangements.Rather, virtually any 3 dimensional arrangement is possible utilizingthe previously discussed production methods.

[0155] Reference herein is made to passage of the decomposition productsof the sacrificial layer through the permanent layer. This broadly isintended to encompass passage in any manner, including though holes orpassages in the permanent layer that may later be closed. However, inone embodiment, passage is by diffusion through a solid permanent layer.

[0156] Furthermore, it should be noted that in the preceding text, rangeand ratio limits may be combined.

[0157] Although the invention has been shown and described with respectto a certain embodiment or embodiments, it is obvious that equivalentalterations and modifications will occur to others skilled in the artupon the reading and understanding of this specification and the annexeddrawings. In particular regard to the various functions performed by theabove described integers (components, assemblies, devices, compositions,etc.), the terms (including a reference to a “means”) used to describesuch integers are intended to correspond, unless otherwise indicated, toany integer which performs the specified function of the describedinteger (i.e., that is functionally equivalent), even though notstructurally equivalent to the disclosed structure which performs thefunction in the herein illustrated exemplary embodiment or embodimentsof the invention. In addition, while a particular feature of theinvention may have been described above with respect to only one ofseveral illustrated embodiments, such feature may be combined with oneor more other features of the other embodiments, as may be desired andadvantageous for any given or particular application.

What is claimed is:
 1. A method of forming an air gap within asemiconductor structure comprising the steps of: (i) using a sacrificialmaterial to occupy a closed interior volume in a semiconductorstructure; (ii) causing the sacrificial material to decompose into oneor more gaseous decomposition products; and (iii) removing at least oneof the one or more gaseous decomposition products by passage through atleast one solid layer contiguous to the interior volume, wherein thedecomposition of the sacrificial material leaves an air gap at theclosed interior volume previously occupied thereby, and the sacrificialmaterial comprises a polymer composition selected from one or morepolycarbonate polymers, polyester polymers, polyether polymers,methacrylate polymers, acrylate polymers, or mixtures thereof.
 2. Themethod of claim 1, wherein the sacrificial material is a polycarbonatepolymer comprises repeating units represented by the general formula of:

where R represents linear and branched (C₁ to C₂₀) alkyl, hydrocarbylsubstituted and unsubstituted (C₅ to C₁₂) cycloalkyl, hydrocarbylsubstituted and unsubstituted (C₆ to C₄₀) aryl, hydrocarbyl substitutedand unsubstituted (C₇ to C₁₅) aralkyl, (C₃ to C₂₀) alkynyl, linear andbranched (C₃ to C₂₀) alkenyl and n is equal to 2 to about 100,000. 3.The method of claim 2, wherein n is equal to 2 to about 10,000.
 4. Themethod of claim 2, wherein n is equal to 2 to about 1,000.
 5. The methodof claim 2, wherein the sacrificial material is selected frompolyethylene carbonate, polyproplyene carbonate or a mixture thereof. 6.The method of claim 1, wherein the sacrificial material is a polyesterpolymer comprising repeating units represented by the general formulaof:

where R represents linear and branched (C₁ to C₂₀) alkyl, hydrocarbylsubstituted and unsubstituted (C₅ to C₁₂) cycloalkyl, hydrocarbylsubstituted and unsubstituted (C₆ to C₄₀) aryl, hydrocarbyl substitutedand unsubstituted (C₇ to C₁₅) aralkyl, (C₃ to C₂₀) alkynyl, linear andbranched (C₃ to C₂₀) alkenyl; x is an integer from 1 to about 20; and nis equal to 2 to about 100,000.
 7. The method of claim 6, wherein n isequal to 2 to about 10,000.
 8. The method of claim 6, wherein n is equalto 2 to about 1,000.
 9. The method of claim 6, wherein x is an integerfrom 1 to about
 10. 10. The method of claim 6, wherein x is an integerfrom 1 to about
 6. 11. The method of claim 1, wherein the sacrificialmaterial is a polyether polymer comprising repeating units representedby the general formula of:

where R²⁰ and R²¹ independently represent linear and branched (C₁ toC₂₀) alkyl, hydrocarbyl substituted and unsubstituted (C₅ to C₁₂)cycloalkyl, hydrocarbyl substituted and unsubstituted (C₆ to C₄₀) aryl,hydrocarbyl substituted and unsubstituted (C₇ to C₁₅) aralkyl, (C₃ toC₂₀) alkynyl, linear and branched (C₃ to C₂₀) alkenyl and n is equal to2 to about 100,000.
 12. The method of claim 11, wherein n is equal to 2to about 10,000.
 13. The method of claim 11, wherein n is equal to 2 toabout 1,000.
 14. The method of claim 1, wherein the sacrificial materialis selected from a polymethyl methacrylate polymer, an acrylate polymeror a mixture thereof where the polymers present each have a molecularweight of about 1,000 to about 1,000,000.
 15. The method of claim 14,wherein the polymethyl methacrylate and/or the acrylate polymer has amolecular weight of about 10,000 to about 500,000.
 16. The method ofclaim 14, wherein the polymethyl methacrylate and/or the acrylatepolymer has a molecular weight of about 100,000 to about 250,000.
 17. Amethod of forming one or more air gaps in a semiconductor structurecomprising the steps of: (I) forming a patterned layer of sacrificialmaterial on a substrate corresponding to a pattern of one or more gapsto be formed in the semiconductor structure; (II) depositing a secondmaterial on the substrate within regions bordered by the sacrificialmaterial; (III) forming an overcoat layer of material overlying thepatterned layer of sacrificial material and second material in theregions bordered by the sacrificial material; (IV) causing thesacrificial material to decompose into one or more gaseous decompositionproducts; and (V) removing at least one of the one or more gaseousdecomposition products by passage through the overcoat layer so that oneor more air gaps are formed within the semiconductor structure, whereinthe sacrificial material is a polymer composition selected from one ormore polycarbonate polymers, polyester polymers, polyether polymers,methacrylate polymers, acrylate polymers, or mixtures thereof.
 18. Themethod of claim 17, wherein the sacrificial material is a polycarbonatepolymer comprising repeating units represented by the general formulaof:

where R represents linear and branched (C₁ to C₂₀) alkyl, hydrocarbylsubstituted and unsubstituted (C₅ to C₁₂) cycloalkyl, hydrocarbylsubstituted and unsubstituted (C₆ to C₄₀) aryl, hydrocarbyl substitutedand unsubstituted (C₇ to C₁₅) aralkyl, (C₃ to C₂₀) alkynyl, linear andbranched (C₃ to C₂₀) alkenyl and n is equal to 2 to about 100,000. 19.The method of claim 18, wherein n is equal to 2 to about 10,000.
 20. Themethod of claim 18, wherein the sacrificial material is selected frompolyethylene carbonate, polyproplyene carbonate or a mixture thereof.21. The method of claim 17, wherein the sacrificial material is apolyester polymer comprising repeating units represented by the generalformula of:

where R represents linear and branched (C₁ to C₂₀) alkyl, hydrocarbylsubstituted and unsubstituted (C₅ to C₁₂) cycloalkyl, hydrocarbylsubstituted and unsubstituted (C₆ to C₄₀) aryl, hydrocarbyl substitutedand unsubstituted (C₇ to C₁₅) aralkyl, (C₃ to C₂₀) alkynyl, linear andbranched (C₃ to C₂₀) alkenyl; x is an integer from 1 to about 20; and nis equal to 2 to about 100,000.
 22. The method of claim 21, wherein n isequal to 2 to about 10,000.
 23. The method of claim 21, wherein x is aninteger from 1 to about
 10. 24. The method of claim 17, wherein thesacrificial material is a polyether polymer comprising repeating unitsrepresented by the general formula of:

where R²⁰ and R²¹ independently represent linear and branched (C₁ toC₂₀) alkyl, hydrocarbyl substituted and unsubstituted (C₅ to C₁₂)cycloalkyl, hydrocarbyl substituted and unsubstituted (C₆ to C₄₀) aryl,hydrocarbyl substituted and unsubstituted (C₇ to C₁₅) aralkyl, (C₃ toC₂₀) alkynyl, linear and branched (C₃ to C₂₀) alkenyl and n is equal to2 to about 100,000.
 25. The method of claim 24, wherein n is equal to 2to about 10,000.
 26. The method of claim 17, wherein the sacrificialmaterial is selected from a polymethyl methacrylate polymer, an acrylatepolymer or a mixture thereof where the polymers present each have amolecular weight of about 1,000 to about 1,000,000.
 27. The method ofclaim 26, wherein the polymethyl methacrylate and/or the acrylatepolymer has a molecular weight of about 10,000 to about 500,000.
 28. Asemiconductor device having one or more air gaps therein produced inaccordance with the method of claim
 1. 29. A semiconductor device havingat least one air gap therein comprising: a substrate; at least oneconductive line or lead; at least one air gap; and an overcoat layer,wherein the at least one air gap is produced in accordance with themethod of claim
 17. 30. The semiconductor device of claim 29, whereinthe at least one air gap has a height which exceeds the height of anadjacent conductive line or lead.
 31. A method of forming air gapswithin a semiconductor structure comprising the steps of: using at leastone sacrificial material to occupy simultaneously or sequentially atleast two closed interior volumes in a semiconductor structure, whereinthe at least two closed interior volumes are on different levels of thesemiconductor structure; causing the at least one sacrificial materialoccupying the at least two closed interior volumes to decompose eithersimultaneously or sequentially into one or more gaseous decompositionproducts; and removing at least one of the one or more gaseousdecomposition products by passage through at least one solid layercontiguous to the interior volume.
 32. The method of claim 31, whereinthe at least one sacrificial material is simultaneously decomposed intoone or more gaseous decomposition products which are remove via passagethrough at least one solid layer contiguous to the interior volume. 33.The method of claim 32, wherein the at least one sacrificial material isselected from one or more norbornene polymers, polycarbonate polymers,polyester polymers, polyether polymers, methacrylate polymers, acrylatepolymers, or mixtures thereof.
 34. The method of claim 33, wherein theat least one sacrificial material is selected from one or morenorbornene polymers.
 35. The method of claim 34, wherein the norbornenepolymer comprises repeating units of the general formula:

wherein R¹ and R⁴ independently represent hydrogen or linear or branched(C₁ to C₂₀) alkyl; R² and R³ independently represent hydrogen, linear orbranched (C₁ to C₂₀) alkyl or the groups:

R⁹ independently is hydrogen, methyl, or ethyl; R¹⁰, R¹¹, and R¹²independently represent linear or branched (C₁ to C₂₀) alkyl, linear orbranched (C₁ to C₂₀) alkoxy, linear or branched (C_(1 to C) ₂₀) alkylcarbonyloxy, and substituted or unsubstituted (C₆ to C₂₀) aryloxy; m isa number from 0 to 4; and n is a number from 0 to 5; and at least one ofsubstituents R² and R¹ is selected from the silyl group represented bythe formula set forth under Ia.
 36. The method of claim 35, wherein inFormula I above, m is preferably 0 or 1 as represented by structures Iband Ic, respectively:

wherein R¹ to R⁴ are as previously defined and at least one of R² and R³is a silyl substituent represented by Ia.
 37. The method of claim 35,wherein R¹ and R⁴ taken together with the two ring carbon atoms to whichthey are attached comprise a repeating unit of the following structure:

wherein B is a methylene group, q is a number from 2 to 6, and R² and R³are as defined above.
 38. The method of claim 35, wherein the norbornenepolymer further comprises hydrocarbyl substituted polycyclic repeatingunits selected from units represented by Formula II below:

wherein R⁵, R⁶, R⁷, and R⁸ independently represent hydrogen, linear andbranched (C₅ to C₂₀) alkyl, hydrocarbyl substituted and unsubstituted(C₅ to C₁₂) cycloalkyl, hydrocarbyl substituted and unsubstituted (C₆ toC₄₀) aryl, hydrocarbyl substituted and unsubstituted (C₇ to C₁₅)aralkyl, (C₃ to C₂₀) alkynyl, linear and branched (C₃ to C₂₀) alkenyl,or vinyl; any of R⁵ and R⁶ or R⁷ and R⁸ can be taken together to form a(C₁ to C₁₀) alkylidenyl group, R⁵ and R⁸ when taken with the two ringcarbon atoms to which they are attached can represent saturated andunsaturated cyclic groups containing 4 to 12 carbon atoms or an aromaticring containing 6 to 17 carbon atoms; and p is 0, 1, 2, 3, or
 4. 39. Thesemiconductor device as set forth in claim 34, wherein the norbornenepolymer comprises repeating units represented by Formula III below:

wherein R⁹ to R¹² independently represent a polar substituent selectedfrom the group: -(A)_(n)—C(O)OR″, -(A)_(n)—OR″, -(A)_(n)—OC(O)R″,-(A)_(n)—OC(O)OR″, -(A)_(n)—C(O)R″, -(A)_(n)-OC(O)C(O)OR″,-(A)_(n)—O-A′-C(O)OR″, -(A)_(n)—OC(O)-A′-C(O)OR″,-(A)_(n)—C(O)O-A′-C(O)OR″, -(A)_(n)—C(O)-A′-OR″,-(A)_(n)—C(O)O-A′-OC(O)OR″, -(A)_(n)—C(O)O-A′-O-A′-C(O)OR″,-(A)_(n)—C(O)O-A′-OC(O)C(O)OR″, -(A)_(n)—C(R″)₂CH(R″)(C(O)OR″), and-(A), —C(R″)₂CH(C(O)OR″)₂; p is 0, 1, 2, 3, 4, or 5; the moieties A andA′ independently represent a divalent bridging or spacer group selectedfrom divalent hydrocarbon groups, divalent cyclic hydrocarbon groups,divalent oxygen containing groups, and divalent cyclic ethers and cyclicdiethers; and n is an integer 0 or
 1. 40. The method of claim 34,wherein the norbornene polymer comprises copolymers comprising acombination of repeating units represented by Formulae I and II,Formulae I and III, Formulae II and III or Formulae I, II and III, whereFormula I is:

wherein R¹ and R⁴ independently represent hydrogen or linear or branched(C₁ to C₂₀) alkyl; R² and R³ independently represent hydrogen, linear orbranched (C₁ to C₂₀) alkyl or the groups:

R⁹ independently is hydrogen, methyl, or ethyl; R¹⁰, R¹¹, and R¹²independently represent linear or branched (C₁ to C₂₀) alkyl, linear orbranched (C₁ to C₂₀) alkoxy, linear or branched (C₁ to C₂₀) alkylcarbonyloxy, and substituted or unsubstituted (C₆ to C₂₀) aryloxy; m isa number from 0 to 4; and n is a number from 0 to 5; and at least one ofsubstituents R² and R³ is selected from the silyl group represented bythe formula set forth under Ia; Formula II is

 wherein R⁵, R¹, R⁷, and R⁸ independently represent hydrogen, linear andbranched (C₁ to C₂₀) alkyl, hydrocarbyl substituted and unsubstituted(C₅ to C₁₂) cycloalkyl, hydrocarbyl substituted and unsubstituted (C₆ toC₄₀) aryl, hydrocarbyl substituted and unsubstituted (C₇ to C₁₅)aralkyl, (C₃ to C₂₀) alkynyl, linear and branched (C₃ to C₂₀) alkenyl,or vinyl; any of R⁵ and R⁶ or R⁷ and R⁸ can be taken together to form a(C₁ to C₁₀) alkylidenyl group, R⁵ and R⁸ when taken with the two ringcarbon atoms to which they are attached can represent saturated andunsaturated cyclic groups containing 4 to 12 carbon atoms or an aromaticring containing 6 to 17 carbon atoms; and p is 0, 1, 2, 3, or 4; andFormula III is

 wherein R⁹ to R¹² independently represent a polar substituent selectedfrom the group: -(A)_(n)—C(O)OR″, -(A)_(n)—OR″, -(A)_(n)—OC(O)R″,-(A)_(n)—OC(O)OR″, -(A)_(n)—C(O)R″, -(A)_(n)—OC(O)C(O)OR″,-(A)_(n)—O-A′-C(O)OR″, -(A)_(n)—OC(O)-A′-C(O)OR″,-(A)_(n)—C(O)O-A′-C(O)OR″, -(A)_(n)—C(O)-A′-OR″,-(A)_(n)—C(O)O-A′-OC(O)OR″, -(A)_(n)—C(O)O-A′-O-A′-C(O)OR″,-(A)_(n)—C(O)O-A′-OC(O)C(O)OR″, -(A)_(n)—C(R″)₂CH(R″)(C(O)OR″), and-(A)_(n)—C(R″)₂CH(C(O)OR″)₂; P is 0, 1, 2, 3, 4, or 5; the moieties Aand A′ independently represent a divalent bridging or spacer groupselected from divalent hydrocarbon groups, divalent cyclic hydrocarbongroups, divalent oxygen containing groups, and divalent cyclic ethersand cyclic diethers; and n is an integer 0 or
 1. 41. The method of claim31, wherein the at least one sacrificial material is selected from oneor more norbornene polymers.
 42. The method of claim 31, wherein the atleast one sacrificial material is selected from one or morepolycarbonate polymers, polyester polymers, polyether polymers,methacrylate polymers, acrylate polymers, or mixtures thereof.
 43. Themethod of claim 42, wherein the sacrificial material is a polycarbonatepolymer comprises repeating units represented by the general formula of:

where R represents linear and branched (C₁ to C₂₀) alkyl, hydrocarbylsubstituted and unsubstituted (C₁ to C₁₂) cycloalkyl, hydrocarbylsubstituted and unsubstituted (C₆ to C₄₀) aryl, hydrocarbyl substitutedand unsubstituted (C₇ to C₁₅) aralkyl, (C₃ to C₂₀) alkynyl, linear andbranched (C₃ to C₂₀) alkenyl and n is equal to 2 to about 100,000. 44.The method of claim 43, wherein n is equal to 2 to about 10,000.
 45. Themethod of claim 43, wherein the sacrificial material is selected frompolyethylene carbonate, polyproplyene carbonate or a mixture thereof.46. The method of claim 42, wherein the sacrificial material is apolyester polymer comprising repeating units represented by the generalformula of:

where R represents linear and branched (C₁ to C₂₀) alkyl, hydrocarbylsubstituted and unsubstituted (C₅ to C₁₂) cycloalkyl, hydrocarbylsubstituted and unsubstituted (C₆ to C₄₀) aryl, hydrocarbyl substitutedand unsubstituted (C₇ to C₁₅) aralkyl, (C₃ to C₂₀) alkynyl, linear andbranched (C₃ to C₂₀) alkenyl; x is an integer from 1 to about 20; and nis equal to 2 to about 100,000.
 47. The method of claim 46, wherein n isequal to 2 to about 10,000.
 48. The method of claim 46, wherein x is aninteger from 1 to about
 10. 49. The method of claim 42, wherein thesacrificial material is a polyether polymer comprising repeating unitsrepresented by the general formula of:

where R²⁰ and R²¹ independently represent linear and branched (C₁ toC₂₀) alkyl, hydrocarbyl substituted and unsubstituted (C₅ to C₁₂)cycloalkyl, hydrocarbyl substituted and unsubstituted (C₆ to C₄₀) aryl,hydrocarbyl substituted and unsubstituted (C₇ to C₁₅) aralkyl, (C₃ toC₂₀) alkynyl, linear and branched (C₃ to C₂₀) alkenyl and n is equal to2 to about 100,000.
 50. The method of claim 49, wherein n is equal to 2to about 10,000.
 51. The method of claim 42, wherein the sacrificialmaterial is selected from a polymethyl methacrylate polymer, an acrylatepolymer or a mixture thereof where the polymers present each have amolecular weight of about 1,000 to about 1,000,000.
 52. A semiconductordevice having one or more air gaps therein produced in accordance withthe method of claim
 31. 53. A method of forming one or more air gaps ina semiconductor structure comprising the steps of: (A) forming apatterned layer of a first sacrificial material on one side of asubstrate corresponding to a pattern of one or more gaps to be formed inthe semiconductor structure; (B) depositing a second material on thesubstrate within regions bordered by the first sacrificial material; (C)forming a first overcoat layer of material overlying the patterned layerof the first sacrificial material and the second material in the regionsbordered by the first sacrificial material; (D) causing the firstsacrificial material to decompose into one or more gaseous decompositionproducts; (E) removing at least one of the one or more gaseousdecomposition products by passage through the first overcoat layer sothat one or more air gaps are formed within the semiconductor structure;(F) forming a patterned layer of a second sacrificial material on thefirst overcoat layer corresponding to a pattern of one or more gaps tobe formed in the semiconductor structure; (G) depositing a thirdmaterial on the first overcoat layer substrate within regions borderedby the second sacrificial material; (H) forming a second overcoat layerof material overlying the patterned layer of the second sacrificialmaterial and the third material in the regions bordered by the secondsacrificial material; (I) causing the second sacrificial material todecompose into one or more gaseous decomposition products; and (J)removing at least one of the one or more gaseous decomposition productsby passage through the overcoat layers so that one or more air gaps areformed within the semiconductor structure, wherein the first and secondsacrificial materials are independently selected from one or morepolycarbonate polymers, polyester polymers, polyether polymers,methacrylate polymers, acrylate polymers, or mixtures thereof.
 54. Amethod of forming one or more air gaps in a semiconductor structurecomprising the steps of: (A) forming a patterned layer of a firstsacrificial material on one side of a substrate corresponding to apattern of one or more gaps to be formed in the semiconductor structure;(B) depositing a second material on the substrate within regionsbordered by the first sacrificial material; (C-1) forming a firstovercoat layer of material overlying the patterned layer of the firstsacrificial material and the second material in the regions bordered bythe first sacrificial material; (C-2) forming a patterned layer of asecond sacrificial material on the first overcoat layer corresponding toa pattern of one or more gaps to be formed in the semiconductorstructure; (C-3) depositing a third material on the first overcoat layerwithin regions bordered by the second sacrificial material; (C-4)forming a second overcoat layer of material overlying the patternedlayer of the second sacrificial material and the third material in theregions bordered by the second sacrificial material; (D′) causing thefirst and second sacrificial materials to decompose into one or moregaseous decomposition products; and (E′) removing at least one of theone or more gaseous decomposition products by passage through theovercoat layers so that one or more air gaps are formed within thesemiconductor structure, wherein the first and second sacrificialmaterials are independently selected from one or more norbornenepolymers, polycarbonate polymers, polyester polymers, polyetherpolymers, methacrylate polymers, acrylate polymers, or mixtures thereof.55. A method of forming one or more air gaps in a semiconductorstructure comprising the steps of: using a sacrificial material tooccupy at least one first closed interior volume in a semiconductorstructure and using a conductive material to occupy at least one secondclosed interior volume in a semiconductor structure, the at least onefirst closed interior volume and the at least one second closed interiorvolume defining at least one gap therebetween; forming an overcoat layerof material on the sacrificial material and the conductive material withthe overcoat material extending into the at least one gap; causing thesacrificial material to decompose into one or more gaseous decompositionproducts; and removing at least one of the one or more gaseousdecomposition products by passage through the first overcoat layer sothat one or more air gaps are formed within the semiconductor structure,thereby yielding overcoated conductive structures.
 56. The method ofclaim 55, wherein the overcoat material completely fills the one or moregaps between the sacrificial material and the conductive material. 57.The method of claim 55, wherein the sacrificial material is selectedfrom one or more norbornene polymers, polycarbonate polymers, polyesterpolymers, polyether polymers, methacrylate polymers, acrylate polymers,or mixtures thereof.
 58. The method of claim 57, wherein the sacrificialmaterial is selected from one or more norbornene polymers.
 59. Themethod of claim 55, wherein the height of the at least one first closedinterior volume exceeds the height of the at least one second closedinterior volume.
 60. The method of claim 55, wherein the height of theat least one second closed interior volume exceeds the height of the atleast one first closed interior volume.
 61. The method of claim 55,wherein the sacrificial material is a polycarbonate polymer comprisesrepeating units represented by the general formula of:

where R represents linear and branched (C₁ to C₂₀) alkyl, hydrocarbylsubstituted and unsubstituted (C₁ to C₁₂) cycloalkyl, hydrocarbylsubstituted and unsubstituted (C₆ to C₄₀) aryl, hydrocarbyl substitutedand unsubstituted (C₇ to C₁₅) aralkyl, (C₃ to C₂₀) alkynyl, linear andbranched (C₃ to C₂₀) alkenyl and n is equal to 2 to about 100,000. 62.The method of claim 61, wherein n is equal to 2 to about 10,000.
 63. Themethod of claim 61, wherein the sacrificial material is selected frompolyethylene carbonate, polyproplyene carbonate or a mixture thereof.64. The method of claim 55, wherein the sacrificial material is apolyester polymer comprises repeating units represented by the generalformula of:

where R represents linear and branched (C₁ to C₂₀) alkyl, hydrocarbylsubstituted and unsubstituted (C₅ to C₁₂) cycloalkyl, hydrocarbylsubstituted and unsubstituted (C₆ to C₄₀) aryl, hydrocarbyl substitutedand unsubstituted (C₇ to C₁₅) aralkyl, (C₃ to C₂₀) alkynyl, linear andbranched (C₃ to C₂₀) alkenyl; x is an integer from 1 to about 20; and nis equal to 2 to about 100,000.
 65. The method of claim 64, wherein n isequal to 2 to about 10,000.
 66. The method of claim 64, wherein x is aninteger from 1 to about
 10. 67. The method of claim 55, wherein thesacrificial material is a polyether polymer comprises repeating unitsrepresented by the general formula of:

where R²⁰ and R²¹ independently represent linear and branched (C₁ toC₂₀) alkyl, hydrocarbyl substituted and unsubstituted (C₅ to C₁₂)cycloalkyl, hydrocarbyl substituted and unsubstituted (C₆ to C₄₀) aryl,hydrocarbyl substituted and unsubstituted (C₇ to C₁₅) aralkyl, (C₃ toC₂₀) alkynyl, linear and branched (C₃ to C₂₀) alkenyl and n is equal to2 to about 100,000.
 68. The method of claim 67, wherein n is equal to 2to about 10,000.
 69. The method of claim 55, wherein the sacrificialmaterial is selected from a polymethyl methacrylate, an acrylate polymeror a mixture thereof where the polymers present each have a molecularweight of about 1,000 to about 1,000,000.
 70. The method of claim 69,wherein the polymethyl methacrylate and/or the acrylate polymer has amolecular weight of about 100,000 to about 250,000.
 71. A semiconductordevice having one or more air gaps therein produced in accordance withthe method of claim
 55. 72. A semiconductor structure comprising: asubstrate; a sacrificial material supported on the substrate; aconductive material supported on the substrate and spaced apart from thesacrificial material; an overcoat layer overcoating the sacrificialmaterial and the conductive material and extending into the one or morespaces between the sacrificial material and the conductive material. 73.The semiconductor structure of claim 72, wherein the sacrificialmaterial is selected from one or more norbornene polymers, polycarbonatepolymers, polyester polymers, polyether polymers, methacrylate polymers,acrylate polymers, or mixtures thereof.
 74. The semiconductor structureof claim 72, wherein the height of the sacrificial material exceeds theheight of the conductive material.
 75. The semiconductor structure ofclaim 72, wherein the height of the conductive material exceeds theheight of the sacrificial material.
 76. A semiconductor structurecomprising: a substrate; a sacrificial material supported on thesubstrate; a conductive material supported on the substrate and spacedapart from the sacrificial material; an overcoat layer overcoating thesacrificial material and the conductive material and extending into theone or more spaces between the sacrificial material and the conductivematerial, wherein the sacrificial material has been removed bydecomposition through the overcoat layer.
 77. The semiconductorstructure of claim 76, wherein the sacrificial material is selected fromone or more norbornene polymers, polycarbonate polymers, polyesterpolymers, polyether polymers, methacrylate polymers, acrylate polymers,or mixtures thereof.
 78. The semiconductor structure of claim 76,wherein the overcoat material of the overcoat layer completely fills theone or more gaps between the sacrificial material and the conductivematerial.
 79. The semiconductor structure of claim 76, wherein theheight of the sacrificial material exceeds the height of the conductivematerial.
 80. The semiconductor structure of claim 76, wherein theheight of the conductive material exceeds the height of the sacrificialmaterial.